This invention relates to volumetric displays and in particular, to stroboscopically illuminated rotating advertising kiosks.
There are many examples of volumetric (volume-filling) autostereoscopic (viewable with the unaided eye) 3-D display systems. For example, U.S. Pat. No. 3,140,415 (Three-Dimensional Display Cathode Ray Tube) discloses a spinning phosphor-coated flat disc which is addressed by a cathode ray gun. The spinning motion allows the display to present luminous points in three dimensions, creating a volumetric autostereoscopic display.
Similar results may be achieved with lasers, as disclosed in U.S. Pat. No. 5,042,909 (Real Time Three Dimensional Display with Angled Rotating Screen and Method) and U.S. Pat. No. 5,854,613 (Laser Based 3D Volumetric Display System). One or more lasers may be used to illuminate regions of a rotating helical screen to produce volumetric imagery.
In U.S. Pat. No. 4,319,805 (Rotary Screen for Receiving Optical Images Particularly Advertising Images), a projector shines imagery onto a rotating screen encased within a spherical enclosure. This requires costly projection optics, a large housing, and suffers from low image quality due to the screen""s motion with respect to the projector.
However, the above volumetric displays use costly components such as lasers, computationally intensive illumination control systems, and difficult-to-manufacture display surfaces. As a result, such systems are not suitable for high-volume, publicly accessible displays such as advertising.
A volumetric display for illuminating a moving object uses a small number of inexpensive components to provide eye-catching visual effects. The resulting volumetric display is inexpensive, robust, and operable in a variety of both indoor and outdoor advertising environments.
In the volumetric display, a strobe source illuminates a moving object at successive instants separated by potentially unequal intervals. These instances of illumination, referred to as xe2x80x9cillumination events,xe2x80x9d are determined by an illumination controller on the basis of the desired visual effect.
To determine the sequence of illumination events, the illumination controller relies on a signal generator that generates both a first signal and a second signal. These two signals are passed to the illumination controller to be interleaved into a sequence of illumination events. In response to the sequence of illumination events, the strobe source illuminates the moving object.
In one aspect of the invention, the signal generator includes a sampling unit that responds to the motion of the moving object, and/or the mechanical phase, or position, of the moving object. This sampling unit thus generates a first signal having a motion frequency associated with motion of the moving object. The sampling unit can, for example, be a divide-by-N block that generates a signal having a frequency obtained by dividing the frequency associated with the motion of the moving object by an integer. Such a sampling unit thus generates a frequency that is proportional to the motion frequency.
In one embodiment, the volumetric display generates entertaining visual effects by generating a second signal having a phase offset relative to the first signal. This causes the moving object to appear to jump discontinuously from one spatial orientation to another spatial orientation. A phase shifted version of the first signal is conveniently generated by interrupting the input to the sampling unit, thereby changing the phase of the its output.
In another embodiment, the second signal has a frequency that differs from the motion frequency associated with the motion of the moving object. Such a signal can conveniently generated by an oscillator tuned to a frequency that is offset from the frequency of the first signal. More complex visual effects can be achieved by providing additional oscillators tuned to frequencies that are offset from the frequency of the first signal by differing amounts.
In an optional feature of the invention, the volumetric display can interact with the viewer. This feature can be implemented, for example, by providing a sensor to detect the presence, position, and/or motion of a person in the vicinity of the display. The illumination controller can then use the output of this sensor to select a suitable visual display.
These and other features of the invention will be apparent from the accompanying detailed description and the figures, in which: